Abstract
Landform changes caused by human activities can directly affect the recharge of groundwater, and are reflected in the temporal and spatial changes in groundwater stable isotope composition. These changes are particularly evident in high-intensity farming areas. In this study, we tested and analyzed groundwater stable isotope samples at different elevations of rice terraces in a typical agricultural watershed of the Hani Terraces, a World Heritage Cultural Landscape in southwest China. Thus, we determined the characteristic variations and factors that influence the temporal and spatial effects on groundwater stable isotopes in the Hani Terraces, which are under the influence of high-intensity farming activities. The elevation gradients of δ18O and δ2H in groundwater are significantly increased due to farming activities. The values were 0.88‰ (100 m)−1 and −4.5‰ (100 m)−1, respectively, and they changed with time. The groundwater circulation cycle is approximately three months. We also used the special temporal and spatial variation characteristics of the groundwater isotopes as a way to evaluate the source and periodic changes of groundwater recharge. In addition, high-intensity rice farming activities, such as ploughing every year from October to January can increase the supply of terraced water to groundwater, thus ensuring the sustainability of rice cultivation in the terraces during the dry season. This demonstrates the role of human wisdom in the sustainable and benign transformation of surface cover and the regulation of groundwater circulation.
Highlights
Groundwater, as the world’s largest freshwater resource, is critically important for irrigated agriculture, and for global food security [1]
The increasing use of groundwater resources for human consumption, agriculture, and industrial uses requires the protection of recharge areas from contamination or land use and land cover changes that may affect the quality and quantity of water in the aquifers [2,3,4]
According to the analysis of the test results for stable isotopes present in 120 groundwater samples during the one-year study period, in the middle-altitude terraces of the Quanfuzhuang catchment of the Hani Terraces, the δ18 O values of groundwater ranged from −9.65% to −3.01%, with an average value of −7.29%, and the δ2 H values ranged from −65.86% to −37.60%, with an average value of
Summary
Groundwater, as the world’s largest freshwater resource, is critically important for irrigated agriculture, and for global food security [1]. The increasing use of groundwater resources for human consumption, agriculture, and industrial uses requires the protection of recharge areas from contamination or land use and land cover changes that may affect the quality and quantity of water in the aquifers [2,3,4]. Climate change has the potential to exacerbate the problem in some regions. It is predicted that anthropogenic climate change will affect rainfall amount and distribution in many parts of the world [5,6,7,8]. Under the influence of both climate change and human activities, depletion of water is widespread in large groundwater systems in both semi-arid and humid regions of the world [1].
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